This application claims the benefit of a Japanese Patent Application No.11-320219 filed Nov. 10, 1999, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to route searching methods and storage media, and more particularly to a route searching method for analyzing timings and delay times of paths which include circuit elements, wirings and the like and through which signals propagate when designing circuits such as LSIs, and to a computer-readable storage medium which stores a program for causing a computer to carry out such a route search process.
2. Description of the Related Art
Route searching methods make a timing analysis, to analyze the timings and the delay times of the paths which include circuit elements, wirings and the like and through which the signals propagate, when designing circuits such as LSIs. Such route searching methods can be categorized into a worst route search and a total route search. In a case where a plurality of paths join, the worst route search propagates, as a route search result, only a calculation result with respect to a worst route. On the other hand, in the case where a plurality of paths join, the total route search propagates, as the route search result, the calculation results with respect to all of the routes.
In addition, in a case where no route search is made, a route is checked every time a calculation is made with respect to the route. When checking the route, a plurality of routes may pass through the same pin depending on the routes, and in this case, the analyzing time of the timing analysis becomes that much longer because calculation conditions are judged a plurality of times with respect to the same pin.
According to the conventional route searching method, the amount of calculations which are made is large because the calculations with respect to the routes are basically made while searching the routes. In addition, the same calculation may be made a plurality of times depending on the routes. As a result, there are problems in that it is difficult to increase the speed of the calculation process in the conventional route searching method, and that a high-speed timing analysis cannot be made by the conventional route searching method.
Accordingly, it is a general object of the present invention to provide a novel and useful route searching method and storage medium, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a route searching method and a storage medium, which can reduce the amount of calculations which are made with respect to the routes regardless of the routes, and can carry out the calculation process at a high speed, so that a high-speed timing analysis can be made.
Still another object of the present invention is to provide a a route searching method used for circuit design, comprising the steps of (a) setting, with respect to each pin, a corresponding flag of a pass flag which indicates that a pin is passed, a searching flag which indicates that a pin is being searched, and a branch flag which indicates that a pin is a branch point, and (b) determining a direction of a route search depending on each flag which is set with respect to each pin. According to the route searching method of the present invention, it is possible to reduce the amount of calculations which are made with respect to the routes regardless of the routes, and to carry out the calculation process at a high speed, so that a high-speed timing analysis can be made.
A further object of the present invention is to provide a computer-readable storage medium which stores a program for causing a computer to carry out a route search for use in circuit design, wherein the program comprises a flag set procedure causing the computer to set, with respect to each pin, a corresponding flag of a pass flag which indicates that a pin is passed, a searching flag which indicates that a pin is being searched, and a branch flag which indicates that a pin is a branch point, and a determining procedure causing the computer to determine a direction of a route search depending on each flag which is set with respect to each pin. According to the computer-readable storage medium of the present invention, it is posisble to reduce the amount of calculations which are made with respect to the routes regardless of the routes, and to carry out the calculation process at a high speed, so that a high-speed timing analysis can be made.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.